The invention relates to a valve device in a connection piece comprising a flow channel which is open at its front and rear ends and wherein a valve body is arranged which can be brought into its opened position by means of an axially displaceable sliding member.
Generally, connection pieces with valve device are installed in a conduit whose channel is to be transmissive in one direction and closed in the opposite direction. The term "conduit" is meant to comprise rigid and flexible cannulas as well as flexible catheters placed in the body of a patient on one end and hose lines of infusion and transfusion devices, pressure measuring conduits as well as syringes at the other end of the connection piece, the valve device being intended for permitting an unhindered supply or collection of liquid and for effecting an automatic closure when the desired liquid flow stops, so that neither body secretion contaminates the surroundings of the connection piece nor air enters into the body of the patient. Both is dangerous for the patient because it gives rise to bacterial infections and the danger of embolism, and the former may also harm the operator by the transfer of germs.
In an arterial puncture, e.g., such valve devices have the task of holding back the blood located in the catheter with an over-pressure 100-200 mm Hg with respect to atmosphere when the sharpened steel cannula is withdrawn from the catheter after a successful puncture of the artery. Furthermore, the valve must open and permit the flow of blood or a flowing medium as soon as the Luer cone of a connection conduit is connected to the connection piece in order to collect blood samples or to measure the blood pressure via a liquid column.
From German Patent DE 28 17 102 C2, a connection piece with a valve device is known, wherein the valve body consists of a disc of elastomer material with a central slot. In the flow channel, a body being displaceable relative to the disc is supported, which is advanced by the connection cone of an infusion tube and at least partially penetrates the slot when in advanced position in order to spread and keep it open. Upon release of the sliding portion from the connection cone, the elastically deformable disc is to press back the sliding portion, the slot being intended to sealingly close. The closing speed and impermeability of the valve device depend on the readjusting capability of the disc material and the soundness of the slot flaps. Therefore, the effectiveness is reduced by material fatigue. The latter results from repeated opening of the valve device during a long-term use of the connection piece. In addition, it becomes noticeable when using the arrangement, e.g., in an aspirating set with an enclosed steel cannula. In this case, the steel cannula deforms the closed slot lips over a longer period of time, and by the plastic deformation, a hole is created which does not close after withdrawal of the steel cannula, so that body secretion escapes to the outside through the hole in the slot closed per se. Besides, the known valve device is not reliable at higher internal pressures, e.g., arterial pressure (pressure of 200 mm water column), because there is the danger that the internal pressure curves the slotted center of the disc outwards, so that the slot lips do not firmly abut each other on their entire thickness but diverge outwards. Thereby, the sealing surface is reduced such that the arterial pressure can press blood to the outside and a medium for bacterial growth is created, which is carried on into the patient and imports bacterial infections.
A valve device known from European Patent Application EP-A-0 261 317 also operates with a push-open mechanism, and its closing efficiency depends on the restoring capability of the valve body configured as a closed elastomer disk. With its inner surface, the elastomer surface lies upon a bearing tip arranged in the flow channel, and a sliding member comprising two fork legs pressing against the edge zone of the elastomer disk to press it away from an annular valve seat in order to open the flow channel acts against its outer surface. Although this known valve device is tight in backflow direction even at high internal pressures, it does not unblock a central channel through which an elongate object such as a steel cannula, a guide wire or a catheter could be guided, and therefore, it is unsuitable for this broad medical product range.